The present invention relates to improving the efficiency of a combustion device by optimizing the concentration or amount of a combustion characteristic in the combusted gas. In another aspect, the invention relates to a method and apparatus for improving the efficiency of a combustion device by adjusting the flow of air to burners contained in the combustion device in response to a measured combustion characteristic of the combusted gas.
Combustion devices such as furnaces, boilers, ovens, or stoves are devices in which heat energy is transferred to a charge or feed in a controlled manner. The typical combustion device takes the form of a metal housing lined with heat-conserving refractory. The charge or feed can enter as a solid, liquid or gas and may or may not be transformed to a different state. The charge or feed can be carried through the combustion device continuously through metal tubes or troughs or may be batch-heated. The functions of combustion devices include, but are not limited to, 1) heating or vaporizing the charge; 2) providing heat of reaction to reacting feeds (such as in a cracking reaction) and 3) providing an elevated and controlled temperature for the physical change of charge materials.
An example of a combustion device is a hydrocarbon cracking furnace which transfers heat in a controlled manner to a hydrocarbon, such as ethane, propane or butane, for conversion to olefins. The typical air flow burner adjustment method for such furnaces is based on furnace draft measurements, flame appearance and volume percent oxygen in the stack outlet gas. This procedure can lead to inefficient furnace operation wherein the oxygen level in the stack outlet gas is low, but the heat used for high economic value processes is also low. This can occur if significant fuel combustion and heat transfer occurs in the secondary heat recovery section, higher in the furnace (nearer the stack) and not in the lower section of the furnace where the highest economic value can be realized from the heat transferred to the charge materials.
Thus, it would be clearly desirable to provide a method and/or apparatus for controlling the operation of a combustion device which results in more efficient operation of the combustion device through maximizing heat transfer to charge materials.
It is an object of the present invention to provide a method of optimizing the efficiency of a combustion device.
A further object of this invention is to provide an apparatus to be used for optimizing the efficiency of a combustion device.
It is yet another object of this invention to provide a method and/or apparatus for optimizing the efficiency of a furnace by maintaining the concentration of a combustion characteristic of the combusted gas, from at least one burner assembly contained therein, within a predetermined range by adjusting the flow of air to at least one burner assembly in response to measured combustion characteristic concentrations.
According to a first embodiment of the present invention, a method of optimizing the efficiency of a combustion device comprising at least one control zone, with each control zone comprising at least one burner assembly, is provided and comprises the steps of:
a) individually supplying fuel to each of the burner assemblies in each of the control zones;
b) individually measuring a combustion characteristic of the collective combusted gas from the burner assemblies in each of the control zones; and
c) individually adjusting the flow of air to each of the burner assemblies in each of the control zones in response to the value of the combustion characteristic corresponding to each of the control zones to keep the value of each of the combustion characteristics within a predetermined range.
According to a second embodiment of the present invention, a method of optimizing the efficiency of a combustion device comprising at least one control zone, with each control zone comprising at least one burner assembly, is provided and includes the steps of:
a) individually supplying fuel to each of the burner assemblies in each of the control zones;
b) individually supplying primary air to each of the burner assemblies in each of the control zones for mixture and at least partial combustion with the fuel supplied thereto thereby producing a separate intermediate combustion product for each of the burner assemblies;
c) individually supplying secondary air to each of the burner assemblies in each of the control zones for mixture with the intermediate combustion product for further combustion thereby producing a combusted gas stream for each of the plurality of burner assemblies;
d) individually measuring a combustion characteristic of the collective combusted gas from the burner assemblies in each of the control zones; and
e) individually adjusting the flow of primary air and individually adjusting the flow of secondary air to each of the burner assemblies in each of the control zones in response to the value of the combustion characteristic corresponding to each of the control zones to keep the value of each of the combustion characteristics within a predetermined range.
According to a third embodiment of the present invention, a combustion device is provided comprising:
a) at least one control zone comprising at least one burner assembly;
b) at least one gas analyzer operably related to each of the control zones for receiving and analyzing samples of combusted gas from the control zones;
c) each of the burner assemblies comprising:
i) a fuel introduction means for introducing fuel into the burner assembly;
ii) a primary air introduction means for introducing primary air into the burner assembly for mixture and at least partial combustion with the fuel, thereby producing an intermediate combustion product; and
iii) a secondary air introduction means for introducing secondary air into the burner assembly for mixture and further combustion with the intermediate combustion product, thereby producing a combusted gas stream for each of the burner assemblies; and
d) control means operably related to the primary air introduction means, the secondary air introduction means, and the at least one gas analyzer, for adjusting the flow of primary air and the flow of secondary air to each of the burner assemblies in each of the control zones through the primary air introduction means and the secondary air introduction means, respectively, in response to the value of a combustion characteristic measured in the collective combusted gas streams corresponding to each of the control zones.
Other objects and advantages will become apparent from the detailed description and the appended claims.